Jeremy Forrest, of London, had not been charged with sex offenses until he admitted them in court before sentencing, the BBC reported Friday.
Forrest did not speak in his own defense during the eight-day trial. His attorney, Ronald Jaffa, told the court the teacher had been in an unhappy marriage and suffered from depression.
While tutoring the girl in math at his home, Forrest realized the teenager had a crush on him, the attorney said. The teacher abducted the girl and took her to France.
"He unfortunately fell in love and crossed the line at a time when he was in a very low position and depressed," Jaffa said.